Liquid content indicating container



Jan. 23, 1968 D. w. HOLDSWORTH 3,364,733

LIQUID CONTENT INDICATING CONTAINER Filed Jan. 16,- 1964 1 9 1, 9 I fi'YI 21M, wag

United States Patent 3,364,733 LIQUID CONTENT INDICATING CONTAINERDennis W. Holdsworth, Lincoln, Mass, assignmto Comstock & Wescott, Inc.,Cambridge, Mass., a corporation of Massachusetts Filed Jan. 16, 1964,Ser. No. 338,190 4 Claims. (Cl. 73-73) ABSTRACT OF THE DISCLOSURE Adevice for indicating the quantity of fuel remaining in a cigarettelighter. A light transmitting rod extends through the fuel containerbetween windows on opposite sides thereof and is shaped in such a waythat a window appears dark when the fuel supply is abundant and lightwhen the fuel supply is exhausted.

This invention relates to containers of liquids, such as fuels, andparticularly to a container which indicates its liquid content.

For example, most cigarette lighters, for reasons of appearance anddurability, are made with an opaque, metal case which conceals theamount of fuel available. Even in lighters having transparent cases andan absorbent filler it is diflicult to determine visually the degree ofsaturation of the filler when the fuel is nearly expended.

Lighters have been proposed which have a glass window frosted on itsinside so that when wetted by fuel the window is transparent or highlytranslucent. Then ambient light entering the window from outside thelighter will be transmitted into and absorbed within the lighter givinga somewhat different indication than when light is reflected from thedry frosted surface. However, after a few fillings most lighter fuelsdeposit a waxy constituent which prevents the frosted side of the glassfrom changing translucency and indicating fuel content.

Accordingly, it is an object of the present invention to provide a wayof indicating liquid content, such as the amount of fuel in a lighter,which gives a clear or quantitative indication, and which is notadversely affected by deposited constituents of the liquid.

According to the invention a liquid container comprises wall meansforming a liquid compartment and at least two windows, and optical meansforming an indirect light path through said compartment between saidwindows, said optical means being shaped to transmit light between saidwindows when said compartment is dry, and to pass light into saidcompartment when it is wet, thereby to indicate the liquid content ofsaid container.

For the purpose of illustration typical embodiments of the invention areshown in the accompanying drawing in which:

FIG. 1 is a front elevation of one form of cigarette lighter accordingto the invention;

FIG. 2 is a section on line 2-2 of FIG. 1;

'FIG. 3 is an enlarged fragment of FIG. 2 showing a side elevation of anoptical prismatic element;

FIG. 4 is a front elevation of the prismatic element of FIG. 3;

FIG. 5 is an enlarged view like FIG. 3 showing another form of prismaticelement; and

FIG. 6 is a front elevation of the prismatic element of FIG. 5.

The cigarette lighter shown in FIGS. 1 to 4 comprises an outer housingbottom 1 connected to a cap 2 by a hinge 3. An inner housing 4telescopes into the bottom 1. The inner housing 4 has side walls 6 andend walls 7 forming a fuel compartment 5 filled with a fuel absorbentfiller 8 such as cotton Wadding. At the top of the inner housing 4 is achimney 9 into which a wick 11 extends from the absorbent filler 8. Aspark wheel 12 is mounted on the chimney 9 adjacent the wick 11. Aconventional flint feed tube, omitted for the purposes of clarity,extends from the lower end of the inner housing 4 through the filler 8to the spark wheel 12.

As shown in FIGS. 1 to 4 the outer housing bottom 1 has laterallyopposed outer circular windows 13 inside of which the inner housing 4has slightly larger rectangular windows 14. Fitted between the innerhousing windows 14 is an optical prismatic element 16 which extendsthrough, and is surrounded by, the fuel absorbent filler 8. In lightershaving only one housing element to form the fuel compartment, theprismatic element would extend between the outermost windows of thehousing.

The prismatic element 16 has shoulders 17 which engage the rectangularwindows 14. From the shoulders 17 the prismatic element extends at anangle of 45 so that two sets of polished, parallel surfaces 18 and 19are at to each other. Either of the two surfaces 18, both backed by thefiller 8, can reflect ambient light inside of the prismatic element ifthe fluid medium beyond them differs considerably in refractive index.With a prismatic element made of a glass such as Pyrex or an acrylicresin having refractive indices in the order of 1.5 A. to 1.9 A., thiscondition exists when the filler is dry and the medium is air. Then,light entering either end of the prismatic element 16 is reflected fromthe polished surfaces along an indirect, folded light path 21 betweenthe two windows 14, as shown in FIG. 2. A smoker, who would naturallyhold the lighter toward a light source, would then see light in thewindow nearest him, indicating a lack of fuel.

On the other hand, if the fuel compartment 5 is sufficiently full offuel to submerge the prismatic element, or if the filler 8 issufliciently wetted adjacent the surfaces 18 and 19, then the refractiveindex so closely approximates or approaches that of the glass or acrylicelement that its surfaces pass substantial light into the fuelcompartment by refraction. As shown in FIG. 3 any light reflected at thefirst surface 18 may be passed into the fuel compartment at the surfaces19 and 18 further along the folded light path. Light is absorbed in thefiller by the multiple refractions so substantially that the exit windowappears black thus providing a markedly contrasting indication to thatwhen the dry fuel compartment allows light to be reflected betweenwindows.

Since the filler 8 tends to dry toward its lower end below the prismaticelement 16, the appearance of the exit window will turn from black(complete non-transmission) through various shades of grey to a lightshade (high transmission) before fuel is completely exhausted. Asomewhat more quantitative indication is given if the filler is coloredred, for example. When the filler is substantially moist, that is onehalf to three quarters full, light is almost completely absorbed and theexit window is black. When the filler becomes only slightly moist atabout 15% saturation, the exit window turns a red color which is easilydistinguished from the black, full indication or the white, emptyindication.

In contrast to a frosted window the polished surface of the presentprismatic element retains its indicating function when coated with awaxy deposit. (Herein the term polished is meant to apply to surfacesmolded to a good optical smoothness.) Whereas the effect of a waxdeposit on a frosted surface is to cause the surface to transmit lightsubstantially the same when wet or dry, a wax deposit on a polishedsurface has little effect on either the reflective or refractiveproperty of the surface, probably because the refractive index of thewax so closely approximates the index of the prismatic element that thewax merely constitutes an extension of the element. The small extentthat the wax does reduce the refractive property of the surfaces 18 and19 is greatly diminished by the multiple refractions, so that the samestriking difference between the dark, full indication and the light,empty indication persists.

As shown in FIGS. 1 to 4 the prismatic element has two arms at 90 toeach other bounded by the surfaces 18 and 19. With this configurationthe shoulders 17 may be easily snap fitted into the windows 14 of theinner housing 4, the walls 7 of the inner housing being sufiicientlyflexible to yield as the element is inserted. The ends of the elementthen fill the windows 14 and close them and the outer windows 13 againstleakage of fuel, although the element ends may be cemented in thewindows 14 if desired.

While a prismatic element of the shape shown in FIGS. 1 to 4 ispreferred, other shaped elements may be used, for example the elongateprismatic element 26 shown in FIGS. 5 and 6. The ends of the elementhave shoulders 27 between which extend polished reflecting surfaces 28and 29. The shoulders fit into windows 34 of a housing 7, which windowsare vertically offset at an angle of 45. Light entering one window willfollow a folded light path 32 being refracted and absorbed at severalpoints in the filler 8 if the filler is wet, or being reflected severaltimes to the exit window if the surfaces 28 and 29 are dry, insubstantially the same way as shown in FIGS. 1 to 4.

Thus, it will be understood that the present disclosure is for thepurpose of illustration only and that this invention includes allmodifications and equivalents which fall within the scope of theappended claims.

I claim:

1. A liquid container comprising wall means forming a liquid compartmentand at least two Windows, a light-absorptive filler body in saidcompartment, and optical means forming an indirect light path throughsaid compartment between said windows, said optical means being shapedto transmit light between said windows when said compartment is dry, andto pass light into said compartment and filler when it is wet, therebyto indicate the liquid content of said container and wherein said filleris colored thereby to color the light transmitted between said windowswhen said filler is almost dry.

2. A cigarette lighter comprising a housing including opposed, opaquewalls forming a compartment for fuel of predetermined refractive indexand having at least two windows respectively in said opposed walls, anda transparent prism system forming a folded light path through saidcompartment between said windows, said prism system having exteriorsurfaces at a substantial angle to said path for reflecting light fromone window along said path to the other window when said compartment issubstantially free of liquid, and said prism system having a refractiveindex close to the index of said fluid,

whereby when said surfaces are wetted by fluid said surfaces pass lightfrom said one window into said compartment where it is absorbed ratherthan transmitted to said other window, thereby to indicate the presenceof fuel.

3. A cigarette lighter comprising a housing including opposed, opaquewalls forming a compartment for fuel of predetermined refractive indexand having at least two windows respectively in said opposed walls, afuel absorbent filler in said compartment, and a transparent prismsystem forming a folded light path through said filler and between saidwindows, said prism system having exterior surfaces opposed by saidfiller and at a substantial angle to said path for reflecting light fromone window along said path to the other window when said filler issubstantially free of liquid, and said prism system having a refractiveindex close to the index of said fluid, whereby when said surfaces arewetted by fluid in said filler said surfaces pass light from said onewindow into said filler where it is absorbed rather than transmitted tosaid other window thereby to indicate the presence of fuel.

4. A cigarette lighter comprising an outer housing leaving two opposedouter windows in its opposite walls, an inner housing slidingly fittingin said outer housing, said inner housing including opposed wallsforming a compartment for fuel of predetermined refractive index andhaving two inner windows respectively in said opposed walls, said innerwindows facing said outer windows, and a transparent prism systemforming a folded light path through said compartment between saidwindows, said prism system having exterior surfaces at a substantialangle to said path for reflecting light from one window along said pathto the other window when said compartment is substantially free ofliquid, and said prism system having a refractive index close to theindex of said fluid, whereby when said surfaces are wetted by fluid insaid compartment said surfaces pass light from said one window into saidcompartment where it is absorbed rather than transmitted to said otherwindow thereby to indicate the presence of fuel, and said prism systemhaving at each end shoulders fitting in and filling said inner windowsthereby to prevent fuel loss through said inner and outer windows.

References Cited UNITED STATES PATENTS 2,190,027 2/1940 Jordan ll61182,454,872 11/1948 Harris 73-73 3,120,125 2/1964 Vasel 73-293 LOUIS R.PRINCE, Primary Examiner.

S. C. SWISHER, Assistant Examiner.

